1. Field of the Invention
The present invention relates to a static var compensator (SVC) that controls reactive power by switching a capacitor bank by using a thyristor switch.
2. Description of the Related Art
In typical reactive power compensators, output reactive power is adjusted step-by-step by switching a plurality of capacitor banks by using thyristor switches. In a conventional reactive power compensator, for example, Japanese Patent Application Laid-open No. S54-011452, to limit the control level per step of the reactive power below a certain value, capacitor banks having unequal capacitances in a binary manner are arranged and these capacitor banks are combined. This technique allows controlling reactive power by a small level per step even with a small number of banks.
The reactive power compensator according to Japanese Patent Application Laid-open No. S54-011452 controls the capacitances of a plurality of capacitor banks by allocating the capacitances in a binary manner, for example, 1:2:4, respectively, so that control is available in seven levels by a level control range of the capacitance 1. However, if the capacitor bank of the capacitance 2 fails, it needs to control only with the capacitor banks of the capacitance 1 and the capacitance 4, so that it results in the maximum level control range 3, consequently, a unit range of control becomes rough. For this reason, voltage fluctuations given to the power system when switching the capacitor banks become large; consequently, there is a problem that an adverse effect, such as a flicker in lighting connected to the same power system, sometimes occurs in some cases.